1. Field of the Invention
The present invention relates to asphalt compositions, asphalt modifiers, methods of making and using such compositions and modifiers, methods of modifying asphalt, and asphalt products.
2. Brief Description of the Related Art
Asphalt is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleum and in some natural deposits. In U.S. terminology, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside North America, the product is called bitumen.
Asphalt binder is a key ingredient in pavements, roofing and waterproofing applications. The primary use of asphalt is in road construction, where it is used as the glue or binder for the aggregate particles, and accounts for approximately 80% of the asphalt consumed in the United States. The most common type of flexible pavement surfacing in the United States is hot mix asphalt (HMA) that may also be known by many different names such as hot mix, asphalt concrete (AC or ACP), asphalt, blacktop or bitumen.
After use of asphalt in road construction, roofing applications, mainly in the form of roofing shingles account for most of the remaining asphalt consumption. Other uses include waterproofing applications.
Asphalt binder as produced by the refining process does not have the desired stiffness modulus for heavy load bearing for use in heavily trafficked pavements such as the Interstate Highways as well as heavily trafficked inner city streets. Until now polymers such as Styrene Butadiene Styrene (SBS) Styrene Butadiene Rubber (SBR), Ethylene Vinyl Acetate (EVA), Fischer-Tropsch Waxes, Elvaloy Ter-Polymers, Natural and Synthetic Latex and Crumbed Tire Rubber and also combinations of one or more of these have been used as asphalt binder modifiers.
Over the past seven years or so, traditional Hot Mix has been under scrutiny due to hydrocarbon emissions, energy cost and difficulties in compaction after long hauls and in cold weather paving. A new technology called “Warm Mix” asphalt emerged around year 2000 and was promoted by the National Pavement Association (NAPA) of the USA and this technology grew very rapidly and a large number of available Warm Mix technologies have emerged in recent years. Currently there are at least 20 such technologies available to the paving industry and the number is growing. The key benefits of Warm Mix are a reduction in asphalt aggregate mixing, transportation, lay down and paving temperatures by between 30° F. to 70° F. and providing benefits such as drastically reduced emissions during production, drastically reduced emissions during paving, energy savings, facilitating longer hauls to paving sites, wider paving window such as early paving in Spring and later paving into Fall and superior compaction over Hot Mix.
Adequate compaction is one of the prerequisites for a long lasting pavement and is difficult to achieve especially with highly modified stiff binders as well as with gap graded mixes such as Stone Mastic asphalt (SMA) and Open Graded Friction Courses (OGFC). Another challenge in achieving adequate compaction is cold climate paving and long haul distances where the mixing plants are located far from the paving sites. Compaction is considered so important by Federal and State authorities that in many cases contractors are awarded bonuses for achieving the target compaction consistently. It is well documented from global field trial and commercial data that Warm Mix applications achieve consistent and on target compaction even in cold weather and with difficult mixes. Also, enhanced compaction through Warm Mix applications a significant development since stiffer binders are being paved to carry the heavier loads and increasing numbers of vehicles on the roads.
Another major development that has emerged in recent years is the issue of personal heath and the related hydrocarbons exposure to paving crews and the motoring public. There is a strong movement to reduce such emissions and Warm Mix technology provides the scope to achieve the targeted new permissible emissions levels. Also, in the context of Green House emissions, there is a strong movement to limit greenhouse gas emissions by asphalt mixing plants as a contribution to limiting this major problem. In Europe the limitations are in place already forcing the paving industry to use green fuels and reduce usage of fuel making Warm Mix the technology of choice. In the USA the use of Warm Mix is gaining momentum at an accelerating pace.
The unpredictable surges in fuel cost have made the energy cost of running asphalt mixing plants a severe cost burden. Warm Mix achieves on average about a 20% savings in energy cost and this is a substantial reduction aside from the benefits of reduced stack emissions from the reduced volume of fuel required for the same tonnage of output by Warm Mix over Hot Mix.
Several technologies are presently in use or in trials or in development as Warm Mix technologies and these may be classified into the following categories: (a) hard waxes such as Fischer-Tropsch® Waxes; (b) surfactants such as a combination of anti-strip agent and other organic additives, and surfactants plus water solution; (c) foaming technologies incorporating hydrated alumino-silicates; (d) foaming technologies incorporating the use of water either into a portion of the fine aggregate feed (such as the Low Energy Asphalt process) or direct atomization of water into the hot binder (such as the Double Barrel Green process).
A major concern of the Warm Mix process is the risk of moisture damage and this is being studied with earnest to assess this risk potential. Firstly, since Warm Mixes are produced at lower temperatures, there remains the risk that the aggregates are not completely dried as with Hot Mix. Secondly, there is the temptation to push Warm Mix to the ultimate limits without any proven data on moisture sensitivity and this may expose potential such risk even further. Thirdly, the use of water as the foaming agent is questionable since it has long been established that if water is left on the surface of the aggregate it will reduce the adhesion of the asphalt binder on to the aggregate causing adhesive failure with time. Also any water present in the binder will reduce the cohesive strength of the asphalt binder over time and cause cohesive failure.
U.S. Pat. No. 4,267,085, issued May 12, 1981 to Katoh et al., discloses injection materials for railroad track beds. Specifically, in a railroad track bed an injected layer is formed between the railroad ties and the roadbed so as to protect the latter. The injected layer is composed of an injection material injected through openings formed in the tie. The injection material has a viscosity below 30 poise at a temperature not higher than 200.degree. C. before hardening, and when hardened it has a compressive stress at 10% strain of 0.4 to 30 kg/cm.sup.2 at a compressive strain rate at 40.degree. C. of 1.5% per minute. The blend material may include asphalt and a low molecular weight polypropylene having a molecular weight of 500-8000 or a high molecular weight polypropylene having a molecular weight of 10,000-100,000.
U.S. Pat. No. 5,952,412 to Greenberg, et al., issued Sep. 14, 1999 for pelletized rubber, discloses rubber pellets made of an amount of vulcanized rubber and an amount of binder, with the vulcanized rubber preferably being discarded rubber. Additionally discloses that the rubber pellets will preferably contain an amount of filler materials which are plastic or rubber or combinations thereof so that the preferred rubber pellet contains an amount of rubber equal to between about 50% and about 95% by weight of the rubber pellet, an amount of filler material equal to between about 0 and about 45% by weight of the rubber pellet, and an amount of binder equal to between about 5% and about 10% by weight of the rubber pellet. Further discloses that the rubber pellets are used in the formation of asphalt and are desirable because they provide necessary constituents to the asphalt and allow for elimination of equipment and separate ingredient addition steps from the asphalt formation process. Further discloses the invention is also desirable because it provides for a way to desirably dispose of waste rubber materials.
U.S. Patent Application Publication No. 20020042477, published Apr. 11, 2002, to Jelling, discloses polymers which have been functionalized so as to be able to chemically react with polyamines to form adducts containing at least one or more groups consisting of amino, amido, imino, imido, or imidazloyl. Furthermore, the invention teaches processes to prepare these adducts by solution, melt or in-situ methods. A further embodiment of the invention pertains to the use of polyolefin plastomers or elastomers, elastomeric polyethylene-polypropylene, compositions or interpolymers of styrenes olefins, which have been chemically modified so that they react with polyamines to confer to asphalt significantly improved desired chemical and physical properties.
U.S. Pat. No. 6,444,731 to Memon, issued Sep. 3, 2002, discloses a method for manufacturing modified asphalt characterized by adding a dispersion agent such as furfural or vegetable oil to a modifier material and then mixing the modifier material with asphalt. Further discloses that the dispersion agent facilitates dispersion of the modifier through the asphalt to form a homogeneous mixture. Further discloses that a first activator is added to the mixture to produce a devulcanized and stabilized asphalt material having improved rheological, separation and solubility characteristics. Further discloses that a micro activator is also added to the mixture to improve the ductility of the modified asphalt. Further discloses that the modifier material comprises granular crumb rubber or polymer.
U.S. Pat. No. 6,588,974 issued Jul. 8, 2003, and U.S. Pat. No. 6,913,416 issued Jul. 5, 2005, both to Hildebrand, et al., disclose bitumen or asphalt for the production of road surfaces, road surfaces, and method for the preparation of bitumen or asphalt. The bitumen or asphalt contains a proportion of paraffin obtained by Fischer-Tropsch synthesis (FT paraffin). Also disclosed are a road topping with the bitumen and a method for producing a corresponding road topping or roadway covering using the bitumen.
U.S. Patent Application No. 20060223916, by Stuart Jr. et al., discloses et al. Oct. 5, 2006 a modified asphalt composition is provided comprising at least one plastomer, at least one elastomer, and asphalt. More specifically, a modified asphalt composition is provided comprising an oxidized polyethylene, a styrene-butadiene-styrene block copolymer, and asphalt. A hot mix asphalt composition is also provided comprising the modified asphalt composition and aggregate. Processes for producing the modified asphalt composition and the hot mix asphalt composition is also provided as well as articles produced from these inventive compositions.
U.S. Patent Application Publication No. 20070218250, published Sep. 20, 2007, to Kiik et al., discloses roofing material that consists essentially of a substrate, a hot melt material applied to one side of the substrate, an asphalt material coating the other side of the substrate and roofing granules disposed on said asphalt material coated on the substrate. The hot melt material may be polyethylene, polyethylene-vinyl acetate, polypropylene, polyvinylidene chloride, polyester, nylon and mixtures thereof. The asphalt material may include non-asphaltic filler.
U.S. Patent Application Publication No. 20080153945, published Jun. 26, 2008, to Prejean, discloses a polymer-modified asphalt composition comprising an elastomeric polymer blend, a low molecular weight plastomer which may be a polyolefin wax, and an unmodified asphalt. Asphalt compositions of the present invention demonstrate improved elasticity and stiffness compared to conventional polymer-modified asphalt compositions.
U.S. Patent Application Publication No. 20090053405, published Feb. 26, 2009, to Martin, discloses bituminous asphalt binder materials that are modified by the addition of crumb rubber or ground tire rubber and a cross-linking agent are described. In addition, methods are provided for producing a modified asphalt binder containing crumb rubber or ground tire rubber and a cross-linking agent. The modified asphalt binders comprise neat asphalt, crumb rubber, one or more acids and a cross-linking agent. Optionally, the modified asphalt binder may include one or more polymer additives, including, polyethylene (linear or crosslinked) and polypropylene (atactic or isotactic). The crumb rubber may be obtained from recycled truck and/or automobile tires. The addition of crumb rubber in asphalt binders can improve the consistency and properties of the asphalt binders at high and low temperatures. In particular, the modified asphalt binders of the present invention exhibit improved elastic behavior, resulting in improved performance of roads or other surfaces paved using the modified asphalt binder. Road resistance to permanent deformation, fatigue cracking and thermal cracking is improved by use of the modified asphalt binder.
U.S. Patent Application Publication No. 20090054562, published, Feb. 26, 2009, to Martin, discloses in a first aspect, bituminous asphalt binder materials which are modified by the addition of crumb rubber or ground tire rubber are described, and discloses in a second aspect, the present invention is directed to methods of producing a modified asphalt binder containing crumb rubber or ground tire rubber. The modified asphalt binders comprise neat asphalt, crumb rubber, one or more synthetic polymers which may include polyethylene, and one or more acids. The crumb rubber may be obtained from recycled truck and/or automobile tires.
The stability of polymer modified asphalt is generally determined by the Separation test (‘cigar tube test’) ASTM D 7173; Determining Separation Tendency of Polymer from Polymer Modified Asphalt. The closer the temperature between the top and the bottom of the cigar tube, the higher the stability. The guidelines as issued by the American Association of State Highway and Transportation Officials (AASHTO) are utilized in many asphalt road formulations. The AASHTO has standardized test designations in the form of T ### for standard laboratory specifications. For example, the AASHTO Cigar Tube Test is T 53. SBS is regarded as the gold standard benchmark for modifying asphalt, with SBS modified asphalt having a cigar test of 2° C. (3.6° F.) temperature differential. Recent price spikes and shortages of SBS have led to a search for other polymers as replacements for SBS in order to modify asphalt. However, while cheaper and/or more available replacement polymers can be found, the stability of the replacement polymers has generally been disappointing. For example, ground tire rubber (GTR) modified asphalt will have a cigar tube test result of 30° F. difference or worse. Some departments of transportation will allow a cigar test result as high as 15° F., while others sometimes waive the 2° C. requirement entirely. However, future trends point to the enforcement of 2° C. (3.6° F.) cigar tube standard, meaning that either SBS will have to be used, or a suitable replacement found.
All of the patents, publications, articles and/or materials cited in this specification, are herein incorporated by reference.
However, in spite of the above advancements, there still exists a need in the art for asphalt compositions and products, and to methods of making and using such compositions and products.
This and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.